Technical points concerning black seabream farming
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**I. Introduction**
**1. Biological Characteristics**
Black sea bream, also known as black crickets, are elongated and flattened fish with a body length typically ranging from 20 to 30 cm and a weight between 100 to 300 grams. Their head is pointed, with long mandibles that extend beyond the maxilla. The vomer and cheekbone have fine teeth, and there is a distinct black line on the maxilla. The back of the head is low, while the dorsal fin is pointed. They have large, high-set eyes, with the space between them approximately equal to the eye diameter. A single spine is present at the lower edge of the orbital bone. The dorsal fin has 13 spines and 12 soft rays, while the caudal fin is rounded. Their scales are small and round, and their coloration includes gray and brown on the back and sides, with irregular black markings. The chest and belly are gray, while the dorsal fin is dark yellow and the rest of the fins are grayish-black.
These fish are found in the western North Pacific, including the Yellow Sea, Bohai Sea, and East China Sea in China, as well as along the northern coast year-round. They are also distributed in North Korea, Japan, and the southern Okhotsk Sea.
Black sea bream prefer warm waters and typically inhabit shallow rocky areas or seaweed forests. They avoid bright light and tend to live in depths less than 20 meters during their early life stages. As they grow older, they move toward deeper waters but return to shallower areas (around 20-30 meters) during spawning season. These fish do not migrate over long distances, though short movements may occur during spring and autumn when water temperatures change.
**2. Living Habits**
Black sea bream are cold-tolerant, with an optimal temperature range of 8–25°C. They grow most rapidly at 14–22°C. When the water temperature drops below 5–6°C, they stop feeding, and their lethal temperature is around 1°C.
They are carnivorous, feeding on small fish, shrimp, shellfish, and cephalopods. In the Yellow Sea and Bohai Sea, they primarily consume squid, yellow croaker, fangshiyun, yujin fish, sardines, and spot-fish, along with shrimp and octopus. Black sea bream have strong appetites, with young fish consuming up to 7.5% of their body weight daily. Their satiety level reaches about 11%.
**3. Growth**
Black sea bream grow quickly. In cage culture experiments in Changdao County, Shandong, fish measuring 7–18 cm were raised and grew to an average of 25.5 cm and 485 g by November. They continue growing the following year. Growth rate declines after the fifth instar and significantly decreases after the eighth instar. In Yantai, seedlings can reach 250 g in their second year and 600–800 g in the third, while wild-caught fish may reach 400 g in two years and 900–1000 g in three.
**4. Breeding Habits**
Black sea bream spawn in the wild. Males mature at 2–3 years, females at 3–4 years. Spawning occurs between 3–14 years of age, with dominant males aged 3–4 and females 5–7. Spawning usually takes place between November and December, with fertilized eggs developing inside the female. The spawning period in Shandong coastal areas is April–May, peaking in mid-May.
Spawning occurs in sheltered reef areas with smooth currents and fresh water. Larvae hatch freely from the mother, with a total length of 6.2–7.2 mm. After a few days, they begin feeding actively. Juveniles grow to 10.25–15 mm, develop hard fins, and resemble adults. By July–August, juveniles 30–50 mm long can be caught near the coast.
**Economic Importance**
Black sea bream are highly valued for their white, tender flesh with low fat content. They are especially popular when steamed or used in soups. Due to their fast growth and adaptability, they are ideal for cage and commercial aquaculture.
**Aquaculture Status**
Main breeding methods include cage culture in Shandong’s Changdao and Rongcheng regions. They naturally overwinter in northern seas, reducing costs and making them popular among farmers. Farming scale has grown from experimental to hundreds of thousands of fish. In markets like Tianjin and Beijing, prices range from 40–50 yuan/kg. Some units in Lianyungang are preparing for large-scale cage farming next year.
**Economic Benefit Analysis**
With a cage investment of 1000 yuan per unit, seed cost of 2 yuan per fish, a 3-year cycle, and a feed coefficient of 8, the economic returns are significant. Total input includes cage, seed, feed, and labor. Output value is calculated based on market price, resulting in substantial profit. However, the long production cycle (3 years) may deter some farmers.
**II. Breeding Technology**
**1. Broodstock Management**
Artificially cultivated or wild broodstock can be used. Wild fish collected before spawning are often used without bait, though survival rates may be low. Young broodstock produce more larvae with fewer deformities, while older ones may have higher abnormal rates. Optimal broodstock are 4–7 years old, 38–45 cm long, weighing 1–1.5 kg. A 40 cm fish can produce 100,000 eggs, increasing with size.
Broodstock are kept in sea cages or land pools, with a density of 3–5 fish/m³. Feeding with jadefish, sardines, and horse mackerel every other day helps maintain health. Water changes and lighting control are essential to prevent stress.
**2. Larval Collection**
Larvae are collected using overflow tanks and then sorted by volume. Healthy larvae are transferred to rearing ponds.
**3. Larval Rearing**
Water quality and feeding are critical. Larvae are stocked at 8000–15000 per m³. Water temperature is gradually increased to 18°C. Live food such as rotifers, Artemia, and copepods are provided, with adjustments made based on larval development. Feeding practices must ensure adequate nutrition while preventing overfeeding.
**III. Post-Cultivation**
Juveniles are moved to secondary ponds or sea cages once they reach 75–30 mm. Stocking densities vary depending on size, and feeding is adjusted accordingly. Regular sorting and water changes help maintain high survival rates.
**IV. Disease Prevention**
Disease management focuses on maintaining good water quality and proper stocking density. While diseases are similar to those in other fish species, strict monitoring and live bait feeding are key to prevention.
Overall, black sea bream offer promising prospects for aquaculture due to their fast growth, high market value, and adaptability. With proper management, they can become a sustainable and profitable species for coastal farming.